In some environments we are getting reports of a fine powder that has formed on the surface of some posts. This very fine powder is a result of a thin layer of oxidation of the polypropylene. This occurrence is also called chalking. We have received these few reports from arid climates where there is little rain that washes the chalk off the posts.
We add a very concentrated anti-oxidant to our materials to keep this naturally occurring aging of the polymer to a minimum. The additives we use are very effective. The oxide scale will not lead to failure in function or life of the PasturePro post.
As a comparison, some steels are formulated to produce a layer of oxide scale, rust. This oxide scale protects the underlying material from much deeper corrosion. The thin chalking layer reported in the harshest environments will protect the underlying material from further UV exposure and deeper oxidation.
In other climates, like some areas of the Pacific Northwest with significant rain, the intensity of the sun exposure is lower and the potential for formation of oxide scale is significantly reduced.
We have tested our products in accelerated weather test chambers. In our accelerated weathering tests we simulated high sun exposure and then heavy rain. In this worst case scenario there was no significant diameter loss of the posts.